1. Field of the Invention
The present invention relates to a brake and operation indicator for a high-voltage switch and, more specifically, to apparatus which absorbs and dissipates the kinetic energy of a moving contact of a power-cartridge-operated high-voltage switch, while giving an indication that the switch has opened. Concurrently with giving an indication that the switch has opened, the pin may also initiate the operation of associated devices in response to the opening of the switch. The present invention constitutes an improvement of the apparatus described and claimed in commonly assigned U.S. Pat. No. 4,342,978 issued Aug. 3, 1982 in the name of Meister, and the following commonly assigned U.S. patent applications: Ser. No. 188,660, filed Sept. 19, 1980 now U.S. Pat. No. 4,370,531 in the name of Tobin; Ser. No. 179,367, filed Aug. 8, 1980 in the names of Jarosz and Panas; and Ser. No. 179,366, filed Aug. 18, 1980 in the name of O'Leary.
2. Discussion of the Prior Art
U.S. Pat. No. 4,342,978 discloses and claims an interrupting module of a current-limiting fuse having a high continuous current rating. The interrupting module comprises a more or less typical current-limiting section, which includes a spirally wound fusible element embedded in a compacted mass of a fulgurite-forming medium, such as silica-sand. An insulative housing is filled with the sand and surrounds the fusible element. Also within the housing is a normally closed switch. The switch includes a pair of contacts which are relatively movable apart along a fixed line of direction for opening thereof. Each end of the fusible element is electrically connected to one of the contacts, which are, in turn, electrically continuous with end terminals carried by the housing and by which the module is connected to a high-voltage electrical circuit for protection thereof. The impedance of the electrical path through the switch is substantially less than the impedance of the path through the fusible element so that, with the switch normally closed and with the module connected to the protected circuit, the majority of the current in the protected circuit flows through the switch, and not through the fusible element. When a fault current, or other over-current, is detected by sensing facilities, a power cartridge is ignited. Ignition of the power cartridge pressurizes a chamber defined by one of the contacts and by a trailer or piston carried by the other contact, which is movable away from the one contact.
The increase in pressure within the chamber rapidly moves the trailer and the movable contact carrying it away from the one contact to open the switch, thereby rapidly commutating the fault current in the switch to the fusible element, which interrupts the current in a more or less typical fashion. During movement apart of the contacts, the trailer isolates the widening gap between the contacts and the movable contact from the ignition products of the power cartridge which may be conductive. This isolation inhibits or prevents arcing between the separating contacts. Further, in the event any arc does form between the contacts, the trailer moves through a bore within, and co-acts with, an insulative tube or liner for constricting such arc. The trailer and the tube may be made of an arc-extinguishing material which, when subjected to the high heat of an electrical arc, evolves large quantities of cooling, de-ionizing, and turbulent gases, which along with arc constriction are effective to extinguish any arc which forms.
The above-noted commonly assigned U.S. patent applications describe and claim various aspects and improvements of the current-limiting fuse of the '978 patent. The '978 patent and the co-pending U.S. patent applications have in common the separation of switch contacts due to the ignition of a power cartridge or operation of a similar device. The movement of the contact due to ignition of the power cartridge is very rapid and ultimately results in there being imparted to the moving contact a large amount of kinetic energy. It is desirable that the housing for the interrupting module remain integral before, during and after its operation, and, accordingly, it has been determined that some way of bringing the moving contact to a stop without rendering the housing disintegral is desirable. Preferably, stopping the moving contact after it has sufficiently separated from the other contact to open the switch is achieved gradually with a gradual dissipation of its kinetic energy.
It has also been determined to be desirable to provide an indication that the switch of the interrupting module has opened. Since the module, including the fusible element and the switch, are contained within the housing, which is opaque, and cannot be directly observed, it is necessary to provide a visual or other detectable member external to the housing which indicates that the switch has opened. Further, in some use environments it may be desirable that this indicator have the capability of initiating the operation of other devices in response to the opening of the switch.
The present invention relates to the provision of apparatus for both braking and stopping the movable contact of the switch and for giving a visual indication that the switch has opened. The present invention is also concerned with the provision of such apparatus having low cost and simple construction combined with reliable operation. The provision of apparatus to achieve these ends is a main object of the present invention.